Seat belts are particularly effective when they are worn by the vehicle occupants closely upon their bodies and the slack in the seat belts is minimized. However, as this will cause considerable discomfort to the wearers, retractor devices are widely used with seat belts so as to accommodate the movement of the seat belt wearers by using spring loaded winding spools.
As such a retractor device, the emergency lock retractor device has recently come to be widely used so that the movement of the occupant may not be restrained under normal condition but the winding spool may be locked up instantaneously upon detection of deceleration or rapid pay-out of the seat belt resulting from occurrence of a vehicle crash or a sudden braking to ensure an appropriate level of the tension of the seat belt.
However, even when such a retractor device is used, it is desired to minimize the initial slack of the seat belt for the seat belt to function most effectively.
To achieve this goal, various preloader devices have been proposed, such as those disclosed in U.S. Pat. No. 4,840,325 and U.S. Pat. No. 4,864,086 07/030,630, filed Mar. 27, 1987, now U.S. Pat. No. 4,840,325, dated June 20, 1989 and 07/132,257, filed Dec.14, 1987, now U.S. Pat. No. 4,864,086, dated Sept. 5, 1989, respectively, which improve the capability of the seat belt system to restrain a vehicle occupant by clamping a part of the seat belt paid out from the retractor device and pulling the clamped part towards the retractor device in response to a signal from a deceleration sensor for detecting deceleration greater than a certain level acting upon a vehicle. The disclosure of these copending applications are incorporated herein by reference.
On the other hand, a seat belt is useful only when it is worn by the vehicle occupant, and it may therefore prove to be quite useless if the occupant fails to wear it. Therefore, various passive seat belt devices have been proposed, such as the one disclosed in Japanese Pat. publication No. 58-14337 in which an end of a seat belt is automatically moved between a position not to obstruct the boarding and unboarding of the vehicle occupant and another position for restraining the movement of the vehicle occupant, according to the opening and closing action of the vehicle door.
Such a seat belt winding device is typically disposed between a pair of seats. To the end of maximizing the protection of the vehicle occupant, the seat belt is desired to be arranged as closely to the vehicle occupant as possible, and the seat belt outlet of the winding device is desired to be placed lower than the waist of the vehicle occupant. However, a retractor device and a preloader device are required to be equipped to each one of a pair of laterally arranged seats, and placing the seat belt outlet as mentioned above tends to create problems due to various restrictions on layout.